Organocuprate complexes have been a cornerstone of synthetic organic chemistry for more than two decades, and provide a highly efficient means of coupling and derivatizing organic molecules. However, little is known of the structure or mechanism of this important class of compounds. We propose to use static XAFS, time resolved XAFS and WAXS will be used to determine the solution speciation of selected, well characterized organocuprate complexes. The ultimate goal of this work is to characterize the molecular mechanism of organocuprate addition reactions so as to permit the rational design of improved organocuprate reagents, which are very relevant to a wide range of synthetic procedures used for biomolecule and drug synthesis.